2015 Year 10 Genetics LO4 AO

Year 10 Science – Biological Sciences

Learning Outcome 4

RECAP/NEW

DOMINANT/RECESSIVE (RECAP)

• Dominant alleles

stand out in their phenotypic features.

represented in capital letters

• Recessive alleles

repressed/masked/supressed by dominant alleles

represented in small letters

CO-DOMINANCE (NEW)

• Some alleles are equally dominant to each other.

• The genotypes are equally expressed.

Eg: Alleles A & B in red blood cells (RBC).

• New phenotype produced.

Allele AB in RBC.

CO-DOMINANCE (NEW)

Genes IA and IB are co-dominant.

Gene i is recessive i.e. blood group O.

CO-DOMINANCE (NEW)

AGGLUTINATION

White blood cells (wbc) produce antibodies when

a foreign body enters the blood stream.

If the wrong blood types are mixed when giving

transfusions, the blood can clump together or

agglutinate and can clog blood vessels.

This can stop the flow of blood to certain parts of

the body.

ANTIBODIES/ANTIGENS

Proteins produced by the wbc to identify and

neutralise antigens.

②

Foreign substances in body that causes the immune system

to produce antibodies.

①

ANTIBODIES/ANTIGENS

TO AGGLUTINATE OR NOT?

NO AGGLUTINATION (A)


A foreign ‘A’ rbc enters the blood stream.


The wbc arrives to ‘inspect’ this invader.


The wbc releases the anti-B proteins.


The anti-B proteins binds to the A antigens.


The antigen/antibody complex is not complimentary i.e.

the shapes do not match!


Foreign ‘A’ blood is not an invader.


Hence, no agglutination occurs.

NO AGGLUTINATION (O)


A foreign ‘O’ rbc enters the blood stream.


The anti-B proteins binds to the O antigens.


The anti-B proteins are unable to bind.

Blood group O does NOT have antigens!!!


Foreign ‘O’ blood is not an invader.


Hence, no agglutination occurs.

AGGLUTINATION (B)

AGGLUTINATION (B)

A foreign ‘B’ rbc enters the blood stream.

AGGLUTINATION (B)


AGGLUTINATION (B)

The anti-B proteins binds to the B antigens.

AGGLUTINATION (B)

The antigen/antibody complex is complimentary i.e. the

shapes do match!

AGGLUTINATION (B)

! ‘B’ blood is a foreign particle or invader!

AGGLUTINATION (B)

Hence, agglutination occurs!!!!!

AGGLUTINATION (B)

Not good for the body as agglutination blocks parts of the blood

vessels!

INCOMPLETE DOMINANCE

• Some alleles are not more dominant than the other.

• Neither genotypes are equally expressed.

• New phenotype produced.

pink flowers instead of

red or white flowers

Snapdragons

SUMMARY OF INHERITANCE TYPES

R.C. PUNNETT

Quiet & gentle.

Connected Mendelism with statistics.

Visual representation of alleles in the Punnet square.

PUNNETT SQUARES

①

① Alleles from father/mother.

PUNNETT SQUARES

②

② Alleles from mother/father.

PUNNETT SQUARES

③ Predicted outcomes of a genetic cross.

③

PUNNETT SQUARES

④

④Possible combination of alleles.

PUNNETT SQUARES

⑤

⑤ Expression of genotype & phenotype.

PUNNETT SQUARES SUMMARY

①

②

⑤

③

④

③ Predicted outcomes of a genetic cross.

Alleles

from

father/

mother.

Alleles from mother/father.

Expression of genotype

& phenotype.

Possible

combination of

alleles.

PEDIGREE CHART

Parental or

offspring

genotype.

① ②

③

Chances of offspring

inheriting the

trait/disease.

Determine the normal, affected or carrier

of the trait/disease.

PEDIGREE CHART DRAWING RULES

❶ Represent Rowan and Mary’s gender.

Rowan and Mary are married.


❷ Represent Rowan and Mary’s marriage.

Rowan and Mary are married.


❸ Represent Rowan and Mary’s children/off-springs.

Rowan and Mary are married. They have three children – two girls

and a boy.


Males with black

hair (H)

Males with brown

hair (h)

Females with black

hair (H)

Females with black

hair (h)

Black hair (H) is dominant over brown hair (h). Draw a pedigree

chart to show a male with black hair who married a brown hair

that has three children – one son with brown hair, one son with

black hair and one daughter with black hair.

❹


Black hair (H) is dominant over brown hair (h). Draw a pedigree

chart to show a male with black hair who married a brown hair

that has three children – one son with brown hair, one son with

black hair and one daughter with black hair.

❹


A normal man marries a carrier woman. They bore two children

– a carrier daughter and an affected son.

Affected male

Normal male

Affected female

Normal female

OR Carrier female

❺


A normal man marries a carrier woman. They bore two children

– a carrier daughter and an affected son. ❺

HOMEWORK

Year 10 Science – Biological Sciences

2015 Year 10 Genetics LO4 AO

Education

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